I know I can choose "Hidden in menus" and never see the devices again when I install a application. But I don't want my old mobile phones display in my account settings anymore. I have sold those phones already and never use them again!

I had two old Android devices, an HTC Magic and a Nexus S. Before giving them away I factory reset both. But the HTC Magic is no longer listed at Play Store, the Nexus S is.
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Paolo AmorosoJan 24 '13 at 10:13

A funny thing was happen to me: I had a HTC Wildfire S, HTC Desire S and actually a HTC Sensation. The Wildfire S was Hardware bugged and exchanged by the Desire S which I gaved to my wife - both devices still in my market account - when i bouhgt the Sensation they was added as normal to my market, restored a coupple of apps, settings a.e. as well as installed few apps from the market. I recognized a death pixel on my sensation, did therefore a ful factory restore (when you switch on the phone keep the power button pushed and same time the volume down - this is putting you in the service menu - select factory reset with the volume button and press the power button again) then i brought the device to the service to replace it with a new one. After I did the setup again on the new device and WONDER!! the old sensation wasn't in my market account anymore!!! no idea why and how but this was the fact.
Maybe it' neccessary to do the Hard-Factory Reset to remove the device...